1. Field of the Invention
The present invention relates to a method for maintaining virtual connections in packet switching networks and more particularly, this invention relates to maintaining virtual connections in packet switching networks when there is partial interruption of the connecting paths.
2. Description of the Prior Art
Various methods of maintaining virtual connections in packet switching networks are known in the art. One such method is disclosed in German Published Application DE 41 28 939. In this method, when there is a partial interruption, the switching equipment connected to the calling subscriber equipment generates a call request that requests the set up of a virtual connection and transmits this to a second packet switching network via a network interface location connected to the switching equipment. In addition to an address field, an address expansion field as well as an information flag are included in the call request. The transmitted call request contains address information in the address field that identifies the network interface location which is necessary for providing the virtual connection. The address expansion field contains information that identifies the called subscriber station which is to be connected with the virtual connection. The address information contained in the address field of the call request indicates the appropriate network interface location for reconnection with the first packet switching network. A connecting path is defined in the second packet switching network to the appropriate network interface location for connection with the first packet switching network and the call request is forwarded to that location. At the network interface location, the address information contained in the address field and address expansion field are exchanged with one another based on the information flag set in the call request. The virtual connection to the switching equipment connected to the called subscriber equipment is set up based on the address information which is now contained in the address field of the call request. This address information identifies the called subscriber equipment.
As discussed above, the method requires that the second packet switching network be compatible with and support the "address expansion" protocol. Every packet switching network, however, cannot be assumed to be compatible with this feature.
It is thus an object of the present invention to maintain a virtual connection via an additional packet switching network wherein the virtual connection is made without requiring that the additional packet switching network be compatible with a particular signaling procedure or protocol.